<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="js/vue.js"></script>
</head>
<body>
    <div id="app">
           请选择省份
           <select v-model="cityid">
               <option value="">请选择省份</option>
               <option value="1">湖北</option>
               <option value="2">河南</option>
           </select>
    </div>
    
</body>
<script>
    new  Vue({
        el:"#app",
        data:{
            cityid:1 
        },
        watch:{
            cityid(id){
                alert("选择的编号为"+id);

            }
        }
    })


</script>
</html>